1. Technical Field
The present invention relates to an optical apparatus and a projector.
2. Related Art
There is a projector known which comprises an optical modulation device for modulating luminous flux from a light source in accordance with image information and a projection optical apparatus for magnifying and projecting the luminous flux modulated by means of the optical modulation device.
As an optical modulation device, used is an active matrix driving type liquid crystal panel in which liquid crystal is air-tightly contained between a pair of substrates, for example. Typically, an incident side polarizing plate and an exit side polarizing plate, which have a predetermined polarizing axis, for transmitting luminous flux are respectively provided on an incident side and an exit side of luminous flux of a liquid crystal panel.
In a projector comprising the above-mentioned liquid crystal panel, when luminous flux is emitted from a light source, absorption of light by a liquid crystal layer, a black matrix, various kinds of wiring and the like easily causes increase in temperature of the liquid crystal panel and generation of heat of a polarizing plate.
In view of the above, proposed is a technique that a transmission type cooling chamber is provided as a liquid coolant layer between a liquid crystal panel and a polarizing plate and a cooling fluid is poured into the cooling chamber for the purpose of keeping down increase in temperature of an optical modulation device or a polarizing plate (refer to JP-A-H01-159684, for example).
As a cooling structure using a cooling fluid, known is one comprising a cooling plate having a structure that a metal pipe is provided as a coolant flow path between inner surfaces of a pair of oppositely assembled metal plates. Such a cooling plate is manufactured by forming a pipe housing groove larger than the metal pipe in at least one of the pair of metal plates to assemble the metal pipe and the pair of metal plates into one body. In a process of manufacturing the above, the metal pipe is supplied with a pressurized fluid after the above assembly and a diameter of the metal pipe is enlarged so that the metal pipe would be in close contact with the pipe housing groove (refer to JP-A-2002-156195, for example).
In the technique of pouring a cooling fluid between a liquid crystal panel and a polarizing plate, luminous flux for forming an image passes through the cooling fluid. Accordingly, an optical image formed by means of the liquid panel includes an image of a bubble or dust contained in the cooling fluid or a blur of the optical image occurs in accordance with distribution of temperature of the cooling fluid. This is likely to cause deterioration in quality of an image. Further, in the case of deterioration of the cooling fluid, for example, transmittance of luminous flux is deteriorated, and as a result, a fall in illuminance or deterioration in color-reproducibility of the optical image formed by means of a liquid crystal panel is caused.
In the process of manufacturing a cooling plate having a structure that a metal pipe is provided as a coolant flow path between inner surfaces of a pair of oppositely assembled metal plates, the pipe housing groove is formed into a reversely tapered shape with respect to a connecting surface of the metal plate and an edge part (an undercut part) of the groove is dug into the metal pipe in enlarging a diameter of the metal pipe in order to connect the metal plate and the metal pipe.
This requires machining with a special cutting tool for forming the above-mentioned undercut part, and therefore, it is difficult to lower a cost.
Further, the process of enlarging a diameter of the metal pipe should be repeated in plural times for the purpose of making close connection between the housing groove and the metal pipe well. This requires considerable time.
Moreover, when a diameter of the metal pipe is small, enlargement of the diameter is difficult and unevenness in quantity of deformation of the pipe is easily caused. This causes a gap between the pipe and the housing groove, so that cooling performance of a cooling plate is easily deteriorated.